feat: add MC 1.21.9/1.21.10 (protocol 773) version constants and enum values

Register protocol 773 for Minecraft 1.21.9 and 1.21.10 (which share the
same protocol as a hotfix release). Update MCHighestVersion to 1.21.10.

Add 49 new item types (copper tools/armor, shelves, copper chests,
copper golem statue variants, oxidized lightning rods, iron chain, etc.),
2 new entity types (CopperGolem, Mannequin), 38 new block materials,
3 new entity metadata serializer types (CopperGolemState,
WeatheringCopperState, ResolvableProfile), and 6 new packet types
(DebugBlockValue, DebugChunkValue, DebugEntityValue, DebugEvent,
GameTestHighlightPos, CodeOfConduct, AcceptCodeOfConduct).

Chain item/block renamed to IronChain in 1.21.9; old enum values
retained for backward compatibility with older palettes.

Made-with: Cursor

MinecraftClient/Mapping/EntityType.cs

@@ -44,6 +44,7 @@ namespace MinecraftClient.Mapping
         Chicken,
         Cod,
         CommandBlockMinecart,
+        CopperGolem,
         Cow,
         Creaking,
         CreakingTransient,
@@ -99,6 +100,7 @@ namespace MinecraftClient.Mapping
         MagmaCube,
         MangroveBoat,
         MangroveChestBoat,
+        Mannequin,
         Marker,
         Minecart,
         Mooshroom,